Naomi Watts and Liev Schreiber, longtime inhabitants of Manhattan, have relocated to Los Angeles. The Post’s LA correspondent, Richard Johnson, reports the bicoastal duo, who are often seen biking with their kids downtown, were at a public school on LA’s west side the other day, enrolling their son Sasha in kindergarten. Their younger son, Samuel, 4, is still in preschool. While Watts is up for an Oscar for her performance in “The Impossible,” Schreiber is in LA filming Showtime’s “Ray Donovan,” playing the titular tough guy who fixes rich people’s problems but has a problem of his own — his father (Jon Voight) just got out of jail. The series premieres in June.